High throughput inspection system and method for generating transmitted and/or reflected images

ABSTRACT

Inspection system and method for high-throughput inspection, the system and method is capable to generate and sense transmitted and/or reflected short duration beams. According to one embodiment of the invention the transmitted and reflected short duration beams are generated and sensed simultaneously thus provide a reflected image and a transmitted image simultaneously. The reflected and transmitted short duration radiation beams are manipulated either in the frequency domain or are distinctly polarized such that they are directed to the appropriate area sensors. According to another aspect of the invention the system changes the manipulation of a short duration beam of radiation to selectively direct the short duration beam to distinct area sensors.

[0001] The present invention relates to a system and method for highthroughput inspection of an object using short duration reflective andtransmitted radiation beams, such as but not limited to radiation beams.

BACKGROUND OF THE INVENTION

[0002] Systems and methods of inspecting an article to determine thecondition of the article, such as a mark (also referred to as reticle orphotomask) are known in the art. Optical inspection systems and methodsinvolve directing a radiation beam onto an inspected object anddetecting the radiation reflected from the system or the radiationtransmitted through the object.

[0003] The size of transistors is constantly reducing and there is aneed to inspect masks (also known as reticles) with higher resolution.In spite of the required higher resolution there is a need to performoptical inspections in a time efficient manner. There is therefore aneed to provide a system and method for inspection that is characterizedby both high throughput and high resolution.

SUMMARY OF THE INVENTION

[0004] The invention provides a system and method for high throughputoptical inspection, whereas the method includes the steps of: (i)Reflecting a first beam of radiation from one face of an area of theobject to produce a short duration reflected beam and simultaneouslytransmitting a second beam of radiation through the area of the objectsincluding the first face and a second face to provide a short durationtransmitted beam; (II) Sensing the short duration reflected beam and theshort duration transmitted beam and in response generating outputsignals reflecting a condition of the area of the object; (III)Periodically repeating steps (I) and (II) until a predefined portion ofthe object is irradiated; and (IV) Processing the output signals toprovide an indication of the condition of the predefined portion of theobject.

[0005] The invention provides an optical inspection system that has areflected and transmitted radiation paths, that enable short durationreflected and transmitted radiation beams to be simultaneously generatedand directed towards area sensors to simultaneously provide atransmitted and reflected images of the inspected objects. Accordingly,the system and method enable simple comparison between transmitted andreflected images of an area (and accordingly simplify the registrationprocess and even eliminate the need for performing registration betweentransmitted and reflected images) as both a transmitted image and areflected image of an area are taken simultaneously.

[0006] The invention provides an optical inspection system of highthroughput by manipulating either reflected or transmitted beams so thatimages are formed at alternating area detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Further features and advantages of the invention will be apparentfrom the description below. The invention is herein described, by way ofexample only, with reference to the accompanying drawings, wherein:

[0008]FIGS. 1a-1 c are schematic diagrams illustrating opticalinspection systems constructed in accordance with the present invention;

[0009]FIGS. 2a-2 b illustrate transmitted and reflected images of anarea, in accordance to an embodiment of the invention;

[0010]FIG. 3 illustrates a scanning scheme in accordance to anembodiment of the invention;

[0011] FIGS. 4-5 are schematic diagrams of optical inspection systems inaccordance to other embodiments of the present invention; and

[0012]FIG. 6 is a flow chart illustrating a method for inspecting anobject, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] As indicated earlier, the method and apparatus of the presentinvention are particularly useful for optically inspecting photomasks inorder to detect defects in reflecting and/or transmissive areas of thephotomask. It is noted that some photomasks have clear areas and opaqueareas alone, while other photomarsks may include areas that arecharacterized by reflection and/or transmission levels between fullreflection/transmission and zero reflection/transmission. For example, ahalf tone area permits only about % of light to pass through it. Forsimplicity of explanation alone it is assumed that the photomask hasclear and opaque areas.

[0014] Electromagnetic radiation beams may be characterized by theirpolarization. The electric field of a linearly polarized optical wavelies only at a single plain. The electric filed of a circularlypolarized optical wave lie in two orthogonal planes and are phasedshifted by a quarter wavelength (or an odd amount of quarterwavelengths) of the optical wave. Polarizing beam splitters divide anoptical wave that has electric filed in two orthogonal planes into twoorthogonally polarized optical waves. Phase retardation involves makingan optical path length for one out of two orthogonal linear polarizationdifferent than the other. Quarter wave retarders convert linearlypolarized optical waves into circularly polarized optical waves and viceversa. Variable retarders are able to change their retardance andaccordingly are able to change the relative phase shift between theelectrical fields in two orthogonal plains, thus introducing a phaseshift. Variable wave retarders may change their retardance between zeroand a portion of a wavelength. Varaible wave retarders are characterizedby the maximal amount of phase shift they introduce. For example a halfwavelength variable retarder is able to change its retardence betweenzero and half wavelength. Phase retarders such as but not limited toquarter wavelength retarder and polarizing beam splitters are known inthe art.

[0015]FIG. 1 illustrated an optical inspection system 10, in accordanceto an embodiment of the invention. System 10 includes a radiationsource. Preferably the radiation has a wavelength of about 193 nm. It iffurther noted that the radiation source is located below a plane inwhich the inspected object is located, but this is not necessarily so.

[0016] System 10 includes a linearly polarized radiation source 12,controller 14, first quarter wave retarder 11, beam splitter 16, firstreflector 22, stage 60, objective lens 36, beam splitter 24, relay lens26, second quarter wavelength retarder 28, polarized beam splitter 30,optics such as transmissive objective lens 59, first area sensor 32 andsecond area sensor 32.

[0017] It is noted that polarized radiation source 12, first quarterwave retarder 18, beam splitter 16, first reflector 22, objective lens36, transmissive objective lens 59, beam splitter 24, relay lens 26,second quarter wavelength retarder 28 and polarized beam splitter 30define a illumination system having a reflected and transmitted paths.

[0018] Polarized radiation source, such a laser 12 is operable togenerate short duration radiation beams 11 of a linear polarization,such as a horizontal polarization (e.g.—the electrical fields of theradiation beam lie in the XZ plain, while short duration radiation beampropagates along the X axis.). Controller 14, coupled to laser 12, isoperable to control the generation of the short duration radiationbeams, such as beam 11, in accordance to an irradiation pattern (alsotermed illumination pattern). Conveniently, the irradiation patternincludes a series of time spaced pulses. The irradiation pattern isresponsive to various parameters such as the radiation source parameters(usually maximal duty cycle), and required throughput. Those of skill inthe art will appreciate that as the wavelength of radiation pulsescontinues to decrease the complexity and cost of high duty cycle laserssubstantially increases.

[0019] Laser 12 is followed by a quarter wave retarder 11 that producesa circularly polarized (assuming Right Hand Circularly (i.e.—RHC)polarized) short duration radiation beam 13. The RHC polarized shortduration radiation beam 13 is split by beam splitter 16 to a first andsecond short duration radiation beams 15 and 17 respectively. The firstshort duration radiation beam 15 is directed towards first reflector 22to be reflected towards the lower face of the inspected object 8, andespecially towards an lower face of an area AR 9 of the inspectedobject, whereas AR 9 is defined by the cross section of the first shortduration radiation beam 15. It is noted that the intensities of thefirst and second short duration radiation beams 15 and 17 may be equalbut this is not necessarily so.

[0020] The first short duration radiation beam 15 is partiallytransmitted through clear portions of area AR 9 to produce shortduration transmitted beam 21. The second short duration radiation beam17 is partially reflected from opaque portions of area AR 9 to produce ashort duration reflected beam 23. Short duration reflected beam is RHCpolarized, while short duration transmitted beam 21 is LHC polarized, asthe polarization of the former is reversed as result of the reflection.

[0021] Short duration transmitted beam 21 and short duration reflectedbeam 23 are collected by objective lens 36 that is positioned above theupper face of the inspected object 8, whereas AR 9 is located at a focalplane of objective lens 36. Short duration transmitted beam 21 and shortduration reflected beam 23 pass through beam splitter 24 to propagatethrough relay lens 26. Relay lens 26 is operative to match the size ofthe image of AR 9 or, as illustrated by FIG. 3, the size of an image ofa rectangular portion of area AR 9 to the sensing surfaces of areasensors 34 and 32. It is noted that the sensing surface of area sensors32 and 34 are rectangular, while the cross section of the short durationreflected and transmitted radiation beams is circular, but this is notnecessarily so, as the short duration reflected and transmittedradiation beam may be shaped to fit the shape of the sensing area, andvice verse.

[0022] After propagating through relay lens 26 the short durationtransmitted beam 21 and short duration reflected beam 23 pass thoughsecond quarter wavelength retarder 28 that converts the LHC polarizedshort duration transmitted beam 21 and the RHC polarized short durationshort duration reflected beam 23 to a linearly polarized radiation beamin the X direction (also referred to as p-polarized radiation beam) 25and to a linearly polarized radiation beam in the Z direction (alsoreferred to as s-polarized beam) 27. Both beams 25 and 27 are directedtowards polarizing beam splitter 30 that directs the p-polarizedradiation beam 25 towards a first area sensor 32 and directs thes-polarized radiation beam 27 towards a second area sensor 34. Thus, thefirst area sensor 32 receives a transmitted image of AR 9 (or of aportion of AR 9) while the second area sensor 34 receives a reflectedimage of AR 9 (or of a portion of AR 9), as illustrated in FIGS. 2a-2 c.

[0023]FIG. 1a illustrates the propagation of both reflected andtransmitted radiation beams that enable the generation of a reflectedand a transmitted image of an area respectfully, whereas FIG. 1billustrates the propagation of the short duration transmitted radiationbeam alone and FIG. 1c illustrates the propagation of the short durationreflected radiation beam alone.

[0024] Preferably, first area sensor 32 and second area sensor 34 areback illumination CCD area sensors having an array of 1024×1024 sensingelements. The 1024×1024 array is partitioned to multiple segments, forenabling parallel reading of the multiple segments and enhancing thesystem throughput. CCD area sensors are available from several vendors,such as Dalsa, Sarnoff or Feirchild. Typical data readout rates of asingle CCD area sensor range between tens mega pixels per second toseveral hundreds mega pixels per second. Alternative configurations ofdetection elements and segments may also be used, as will be apparent tothose skilled in the art.

[0025] The first area sensor 32 and second area sensor 34 are operableto (a) sense the short duration transmitted beam and the short durationreflected beam, respectively, and, in response, to (b) generate outputsignals reflecting a condition of the irradiated area of the object. Theoutput signals reflect the charge of each sensing element, whereas thecharge is responsive to the intensity of radiation that is incident onthe sensing element. In other words, the output signals of first areasensor 32 represent a transmitted image received by the first areasensor 32, while the output signals of second area sensor 34 represent areceived image received by the second area sensor 34.

[0026] Those of skill in the art will appreciate that other polarizationschemes, such ellipsoid polarization and linearly polarization may beutilized for separating the short duration reflected beam and shortduration transmitted beam.

[0027]FIGS. 2a-2 c illustrate an exemplary area AR 9 and especially arectangular portion 9(1) of AR 9. Portion 9(1) has opaque portions 100,102, 104 and 106, clear portions 101, 103 and 105 and foreign particle110 and 120. The clear and opaque portions are in the form of bright anddark areas in the transmitted image 92 of FIG. 2b while being in theform of dark and bright areas in the reflected image 94 of FIG. 2c.Foreign particle 110 that is located above clear portion 103 can be seenas a radiation fall off (12) in the transmitted image 92 and as a spot(114) that has a different brightness than its surroundings in thereflected image 94. Foreign particle 120 that is located above opaqueportion 104 can be seen as spot 122 in the reflected image 94.

[0028] Referring back to FIGS. 1a-1 c, controller 16 is operable toinitiate the reflection, transmission and sensing of short durationradiation beams until a predefined portion of the object is radiated andis further operable to process the output signals to provide anindication of the condition of the predefined portion of the object.Various signal processing schemes are known in the art, such as acomparison between the reflected image and the transmitted image. Asboth images are acquired simultaneously, there is no need to perform aregistration between these images, thus simplifying the processing stageand improving the accuracy of the image processing.

[0029] Stage 60 is operable to hold the inspected object and translateit such that a predefined portion of the inspected object is illuminatedduring a series of reflection, transmission and detections iterations.The illuminated areas and especially the portions that are later imagedon the area sensors overlap, thus reducing the sensitivity of system 10to mechanical vibrations and for preventing gaps in the coverage of theinspected object. Usually, stage 60 translates the inspected object suchthat a predefined portion of the inspected object is irradiated.Preferably, the inspected object is raster scanned, but other scanningschemes may also be implemented.

[0030]FIG. 3 illustrates a scanning scheme in which the inspected objectis translated along a scan (X) axis and a row of partially overlappingcircular areas 90(m,1)-90(m,n) is illuminated during a series of timespaced short duration radiation pulses. It is noted that a rectangularportion (denoted 92(m, 1)-90(m,n)) of each of said circular areas90(m,1)-90(m,n) is imaged on the sensing surfaces of first area sensor32 and second area sensor 34, but this is not necessarily so. Forexample, the radiation beams may be shaped as to illuminate arectangular area, or the first area sensor and second area sensor mayhave a circular shaped sensing surface.

[0031]FIG. 4 illustrates an optical inspection system 10, in accordanceto another embodiment of the invention. System 110 differs from system10 in that the differentiation between the transmitted and reflectedbeams that generate the transmitted and reflected images is based uponwavelength but not upon polarization. In other words, the short durationreflected radiation beam differs from the short duration transmittedradiation beam by wavelength. It is noted that the generation of shortduration radiation beams of distinct wavelength may be implemented byusing distinct radiation sources, but when dealing with ultra shortradiation pulses (such as picoseconds till nanoseconds radiation pulses)the synchronization between distinct radiation sources is very complex,thus using a single radiation source for generating the short durationradiation pulses is more feasible and much more accurate. Accordingly, asingle radiation source generates a multi-wavelength short durationradiation pulses that are later filtered to split multiple shortduration radiation beams of distinct wavelength.

[0032] As system 110 is based upon wavelength separation, the polarizingand polarization based elements of system 10 (such as first quarter waveretarder 18, second quarter wavelength retarder 28, polarized beamsplitter 30) are replaced by dichronic beam splitter 116 and 130.

[0033] System 110 includes polychromatic radiation source 112 thatgenerates multi-wavelength short duration radiation beams 111, that aredirected towards dichroic beam splitter 116, that splits said beam toprovide a first wavelength short duration beam 115 that is directedtowards first reflector 22, and to provide a second wavelength shortduration beam 117 that is directed towards second reflector 20.

[0034] First wavelength short duration beam 115 is reflected from firstreflector 22, passes through optics, such as transmissive objective lens159, and passes through clear portions of illuminated area AR 9, iscollected by objective lens 36, passes through relay lens 26 and issplit by diachronic beam splitter 130 to two portions 125 and 135. Firstportion 125 passes through first spectral filter 116 and arrives tofirst area sensor 32 and forms a transmitted image of AR 9, while asecond portion 135 is blocked by second spectral filter 114 thus doesnot arrive to second area sensor 34.

[0035] Second wavelength short duration beam 117 is reflected fromsecond reflector 20, is reflected from opaque portions of illuminatedarea AR 9, is collected by objective lens 36, passes through relay lens26 and is split by beam splitter 130 to two portions 127 and 137. Firstportion 127 is blocked by first spectral filter 112 thus does not arriveto first area sensor 32, while second portion 137 passes through secondspectral filter 114 and arrives to second area sensor 34 and forms areflected image of AR 9.

[0036] First and second array sensors 32 and 34 simultaneously send tocontroller 14 electrical signals representative of a transmitted andreflected images of area AR 9, respectively. Controller 14 processes theimages to determine the condition of area AR 9.

[0037] It is noted that polychromatic radiation source 112, diachronicbeam splitters 116 and 130, first reflector 22, relay lens 26 andtransmissive objective lens 159 define an illumination system that has areflective and transmitted radiation paths.

[0038]FIG. 5 illustrates an optical inspection system 210, in accordanceto a further embodiment of the invention. System 210 generates onlytransmitted images but is characterized by a very high throughput.

[0039] It is known in the art that area detectors that include multiplesensing elements, such as area CCD cameras, are limited by their datareadout rate. It is known that although an image is formed in parallelat the sensing elements of a CCD camera, the sensing elements are readin a serial manner. In some CCD cameras the multiple sensing elementsare partitioned to segments, whereas each segments includes sensingelements that are coupled to each other in a serial manner, whereas eachsegment may be read in parallel to the other segment, thus increase theoverall readout rate of the CCD camera, but this may not provide therequired readout rate. Another method for multiplying the data readoutrate involves buffering the sensing element readout within the CCDcamera, but this solution is very costly.

[0040] System 210 enables to increase the throughput of an inspectionsystem by utilizing two CCD cameras while alternating the polarizationof the radiation beam and accordingly alternating the area sensingelement that generates the image.

[0041] System 210 may have a transmitted radiation path alone thatincludes first quarter wavelength retarder 16, a fast variable halfwavelength retarder 50, first reflector 22, stage 60, objective lens 36,relay lens 26, second quarter wavelength retarder 28, polarized beamsplitter 30, first area sensor 32 and second area sensor 34. Firstquarter wavelength retarder 16, fast variable half wavelength retarder50, first reflector 22, stage 60, objective lens 36, relay lens 26,second quarter wavelength retarder 28 and polarized beam splitter 30define a illumination system that has a transmitted radiation path.

[0042] Fast variable half wavelength retarder 50 is able to change thepolarization of the transmitted radiation beam from RHC polarization andLHC polarization, in response to control signals from controller 14. Thechange rates may be adjusted/selected to fit the readout period out ofeach area sensor. It usually ranges between several hundred changes persecond, but this is not necessarily so.

[0043] When the variable half wavelength retarder 50 does not change thepolarization of the radiation beam the transmitted radiation beamarrives to the first area sensor 32, while when the variable halfwavelength retarder 50 introduces a phase shift of half a wavelength,the transmitted radiation beam arrives to the second area sensor 34.

[0044] The timing of beam transmission and electrical transmission toprocessor 14 is illustrated by “N'th cycle”, “(N−1)'th cycle” and“(N+1)'th cycle” reflecting that an image is directed towards secondarea sensor 34 during a (N−1)′th cycle, that an image is directedtowards first area sensor 32 and that output signals (that reflect theimage that is generated during the (N−1)′th cycle) are provided fromsecond area sensor 34 to controller 14 during a N′th cycle and thatduring the (N+1)′th cycle output signals (that reflect the image that isgenerated during the N′th cycle) are provided from first area sensor 32to controller 14.

[0045] Those of skill in the art will appreciate that system 210 mayinclude a reflective path alone, whereas the reflected path includes ahalf wavelength retarder, beam directing elements such as reflectors andbeam splitters.

[0046] If is further noted that the elements of systems 10 and 210 maybe combined, to allow the generation of reflected and transmittedimages, or to allow the generation of transmitted images alone orreflected images alone (when the half wavelength retarder is located ata reflected radiation path).

[0047] Referring to FIG. 6 illustrating a method 400 for inspecting anobject.

[0048] Method 400 starts at step 410 of reflecting a first beam ofradiation from one face of an area of the object to produce a shortduration reflected beam and simultaneously transmitting a second beam ofradiation through the area of the objects including the first face and asecond face to provide a short duration transmitted beam.

[0049] Step 410 is followed by step 420 of sensing the short durationreflected beam and the short duration transmitted beam and in responsegenerating output signals reflecting a condition of the irradiated area.

[0050] Step 420 is followed by step 430 of processing the electricalsignals to provide an indication of the condition of an illuminated areaof the object. Step 430 is followed by step 440 of determining whetheranother illumination is required (e.g.—if the predefined portion wasalready illuminated) and if so—step 440 is followed by step 410 suchthat steps 410-440 are periodically repeated until the predefinedportion of the object is radiated. Else, step 440 is followed by “END”step 450.

[0051] It is noted that FIG. 6 illustrates a method in which theprocessing is done during the illumination and determination steps, butthis is not necessarily so as the electrical signals may be stored andlater on processed.

[0052] It will thus be appreciated that the preferred embodimentsdescribed above are cited by way of example, and that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and sub-combinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofwhich would occur to persons skilled in the art upon reading theforegoing description and which are not disclosed in the prior art.

We claim:
 1. A method of optically inspecting an object for indicatingthe condition of the object, comprising the steps of: (a) reflecting afirst beam of radiation from one face of an area of the object toproduce a short duration reflected beam and simultaneously transmittinga second beam of radiation through the area of the objects including thefirst face and a second face to provide a short duration transmittedbeam; (b) sensing the short duration reflected beam and the shortduration transmitted beam and in response generating output signalsreflecting a condition of the area of the object; periodically repeatingthe step (a) and (b) until a predefined portion of the object isradiated; and processing the output signals to provide an indication ofthe condition of the predefined portion of the object.
 2. The method ofclaim 1 wherein the object is translated along a scan axis during theperiodical repetition of steps (a) and (b); wherein each face of eacharea has a shape that is characterized by a scan axis projection and bya cross scan axis projection; and wherein the scan axis projection andthe cross scan axis projection are substantially equal.
 3. The method ofclaim 1 wherein the object is translated along a scan axis during theperiodical repetition of steps (a) and (b); wherein each face of eacharea has a shape that is characterized by a scan axis projection and bya cross scan axis projection; and wherein the scan axis projection isnot much longer than the cross scan axis projection.
 4. The method ofclaim 1 wherein the short duration transmitted beam and the shortduration reflected beam are sensed by at least one area type sensor. 5.The method of claim 1 wherein the first and second beams of radiationsare generated by a single radiation source.
 6. The method of claim 1wherein the short duration reflected beam and the short durationtransmitted beam are characterized by different polarization.
 7. Themethod of claim 1 wherein the short duration transmitted beam is sensedby a sensor positioned on one side of the object and the short durationreflected beam is sensed by a sensor positioned on another side of theobject.
 8. The method of claim 1 herein the first and second beams arecharacterized by different wavelengths.
 9. The method of claim 1 whereinthe reflected and transmitted beams are ultrahigh frequency radiationbeams.
 10. The method of claim 1 wherein the reflected and transmittedradiation waves are extreme ultra violet radiation beams.
 11. The methodaccording to claim 1, wherein said predefined portion of the objectincludes the whole object.
 12. The method according to claim 1, whereinsaid first and second short duration radiation beams are produced byseparate radiation sources.
 13. The method according to claim 1, whereineach of said first and second beams of radiation is produced by a highintensity radiation source periodically energized for periods of lessthan 1 nanosecond.
 14. The method according to claim 13 wherein a dutycycle of the high intensity radiation source is less than 0.001.
 15. Themethod according to claim 1, wherein the object being opticallyinspected is a photomask having clear areas and opaque areas, and thecondition to be indicated is the presence or absence of defects in saidclear areas and opaque areas of the photomask.
 16. A method of opticallyinspecting an object for indicating the condition of the object,comprising the steps of: selecting an area sensor out of multiple areasensors and determining a manipulation of a short duration beam ofradiation such that a short duration reflected beam is sensed by theselected area sensor; manipulating and reflecting the beam of radiationfrom one face of an area of the object to produce the short durationreflected beam; sensing the short duration reflected beam by theselected area sensor and generating output signals in response;selecting another area sensor out of the multiple area sensors andrepeating a cycle of manipulating, reflecting and sensing until apredefined portion of the object is radiated; whereas during each cycleenabling output signals of a previously selected area sensor to beprocessed; and processing the output signals to provide an indication ofthe condition of the predefined portion of the object.
 17. The method ofclaim 16 wherein the manipulation is performed in the frequency domain.18. The method of claim 16 wherein the manipulation includes polarizingthe short duration beam of radiation.
 19. A method of opticallyinspecting an object for indicating the condition of the object,comprising the steps of: selecting an area sensor out of multiple areasensors and determining a manipulation of a short duration beam ofradiation such that a short duration transmitted beam is sensed by theselected area sensor; manipulating and reflecting the beam of radiationfrom one face of an area of the object to produce the short durationtransmitted beam; sensing the short duration transmitted beam by theselected area sensor and generating output signals in response;selecting another area sensor out of the multiple area sensors andrepeating a cycle of manipulating, transmitting and sensing until apredefined portion of the object is radiated; whereas during each cycleenabling output signals of a previously selected area sensor to beprocessed; and processing the output signals to provide an indication ofthe condition of the predefined portion of the object.
 20. The method ofclaim 19 wherein the manipulation is performed in the frequency domain.21. The method of claim 19 wherein the manipulation includes polarizingthe short duration beam of radiation.
 22. A high throughput inspectionsystem, the system comprising: a illumination system for reflecting afirst beam of radiation from one face of an area of the object toproduce a short duration reflected beam and simultaneously transmittinga second beam of radiation through the area of the objects including thefirst face and a second face to provide a short duration transmittedbeam; at least one sensor for sensing the short duration reflected beamand the short duration transmitted beam and in response generatingoutput signals reflecting a condition of the area of the object; acontroller for periodically repeating the steps of reflecting andsensing until a predefined portion of the object is radiated and forprocessing the output signals to provide an indication of the conditionof the predefined portion of the object.
 23. The system of claim 22wherein the short duration reflected beam and the short durationtransmitted beam are characterized by different polarization.
 24. Thesystem of claim 22 wherein the short duration transmitted beam is sensedby a sensor positioned on one side of the object and the short durationreflected beam is sensed by a sensor positioned on another side of theobject.
 25. The system of claim 22 wherein the first and second beamsare characterized by different wavelengths.
 26. The system of claim 22wherein said first and second short duration radiation beams areproduced by separate radiation sources.
 27. A high-throughput inspectionsystem comprising: a controller, for selecting an area sensor out ofmultiple area sensors and determining a manipulation of a short durationbeam of radiation such that a short duration reflected beam is sensed bythe selected area sensor; a illumination system for manipulating andreflecting the beam of radiation from one face of an area of the objectto produce the short duration reflected beam; at least one sensor forsensing the short duration reflected beam by the selected area sensorand generating output signals in response; whereas the controller isfurther adapted to (i) select another area sensor out of the multiplearea sensors and repeat a cycle of manipulating, reflecting and sensinguntil a predefined portion of the object is radiated; (ii) enable outputsignals of a previously selected area sensor to be processed, during acycle; and (iii) process the output signals to provide an indication ofthe condition of the predefined portion of the object.
 28. The system ofclaim 27 wherein the manipulation is performed in the frequency domain.29. The system of claim 27 wherein the manipulation includes polarizingthe short duration beam of radiation.
 30. A high-throughput inspectionsystem comprising: a controller, for selecting an area sensor out ofmultiple area sensors and determining a manipulation of a short durationbeam of radiation such that a short duration transmitted beam is sensedby the selected area sensor; an illumination system for manipulating andreflecting the beam of radiation from one face of an area of the objectto produce the short duration transmitted beam; at least one sensor forsensing the short duration transmitted beam by the selected area sensorand generating output signals in response; whereas the controller isfurther adapted to: (i) select another area sensor out of the multiplearea sensors and repeat a cycle of manipulating, transmitting andsensing until a predefined portion of the object is radiated; (ii)enable, during each cycle, output signals of a previously selected areasensor to be processed; and (iii) process the output signals to providean indication of the condition of the predefined portion of the object.31. The system of claim 31 wherein the manipulation is performed in thefrequency domain.
 32. The system of claim 31 wherein the manipulationincludes polarizing the short duration beam of radiation.